{"id":251,"date":"2023-09-29T09:48:00","date_gmt":"2023-09-28T23:48:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2023\/09\/29\/the-art-of-electronics-8-why-not-a-simple-emitter-follower-as-the-af-output-circuit\/"},"modified":"2025-07-22T18:02:04","modified_gmt":"2025-07-22T08:02:04","slug":"the-art-of-electronics-8-why-not-a-simple-emitter-follower-as-the-af-output-circuit","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2023\/09\/29\/the-art-of-electronics-8-why-not-a-simple-emitter-follower-as-the-af-output-circuit\/","title":{"rendered":"“The Art of Electronics” #8 — Why Not a Simple Emitter Follower as The AF Output Circuit?"},"content":{"rendered":"
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Click on the image for an easier read<\/div>\n

Back when Dean KK4DAS and I were trying to find a suitable AF amplifier circuit for our High School Direct Conversion receiver project, we were debating what to use as the final. One option was the standard NPN-PNP push-push amplifier (like in Figure 2.53 above) — an advantage with this one was that it would not require an AF transformer. But we decided that this circuit would add complexity to a project that we were hoping to keep very simple. <\/b><\/p>\n

Another option was a simple common emitter amplifier with a transformer in the collector circuit. This worked, and was simpler. We ordered the transformers. <\/b><\/p>\n

In the midst of all this, at the local radio club hams asked us why we just didn’t put a single emitter follower at the output to handle the impedance transformation to an 8 ohm speaker (sort of as in Figure 2.52 above). They were convinced this would work. I was not so convinced and pointed out that we had never seen such a circuit in any of the ham radio literature. If this could be done, why hadn’t the likes of Doug DeMaw and others used this circuit in their many, many rigs? <\/b><\/p>\n

This discussion kind of ended there (we opted for the common emitter transformer circuit), but I have thought about it from time to time. A couple of weeks ago, when I got the second edition of The Art of Electronics, I found the above discussion of the use of this kind of emitter follower circuit. You can see why this circuit has not been used. Just to be sure, I built one in LTSpice. Sure enough, it takes way too much current. <\/b><\/p>\n

Thank you, Horowitz and Hill! <\/b><\/p>\n","protected":false},"excerpt":{"rendered":"

Click on the image for an easier read Back when Dean KK4DAS and I were trying to find a suitable AF amplifier circuit for our High School Direct Conversion receiver project, we were debating what to use as the final. One option was the standard NPN-PNP push-push amplifier (like in Figure 2.53 above) — an … Continue reading ““The Art of Electronics” #8 — Why Not a Simple Emitter Follower as The AF Output Circuit?”<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[112,84,115],"tags":[],"class_list":["post-251","post","type-post","status-publish","format-standard","hentry","category-the-art-of-electronics","category-amplifier-theory","category-audio-amplifiers"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/251","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/comments?post=251"}],"version-history":[{"count":1,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/251\/revisions"}],"predecessor-version":[{"id":254,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/251\/revisions\/254"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=251"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=251"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=251"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}